Posted by The Taint on 9/4/2013 6:35:00 PM (view original):If you're watching the Rangers/A's game right now, you know that if the sun isn't factored into defensive stats in that park, the defensive stats are bullshit. The sun is brutal today and the Rangers have misplayed three fly balls in this inning alone because of it.

still waiting over here, on aisle twelve, for that price-check. anyone else? what will the numbers cost, money-wise? is it a subscription? bi-weekly? comes with a password to the latest numbers from today's ''gamma-ray'' blast, in arlington stadium?

even the_taint might give a few bucks to find out the origins of those 5 errors today. but, probably not. maybe. a guess, but, tell us how much they want for those numbers? do bookies buy them, u think? ooh.

yes. which metric? the one measuring an mvp when one is needed? or the one that evaluates and enumerates a single play? or the one that goes forward and predicts what should be expected? or the one that always goes backwards by fifty?

which one captures it best? lets end the mystery and buy the numbers. help please.

Posted by bad_luck on 9/4/2013 6:01:00 PM (view original):Are you asking why sample sizes play a large role in the reliability of a stat?

You know exactly what I'm asking. Don't play dumb.

Per you:
1) We need three seasons of fielding data to get a good "feel".
2) But not with hitters because they get 700 PA while fielders get 150-200 chances.

So, if it's a numbers game, and you're saying it is, do we need three years of fielding data for all positions? If so, why? As I recall, some positions get a lot more opportunities to field the ball. Is it 600 chances? What's the number?

1) We need roughly three full seasons of UZR to reliably conclude that the number is a good indicator of the player's true talent. That three seasons isn't exact, it's just a guideline.

2) When Taylor Teagarden posts a 1.200 OPS over 50 plate appearances, do you expect that to continue? Or do you consider it a fluke due to the sample size?

2b) Assuming that you consider it a fluke, would you stop using OPS because it doesn't reliably indicate a player's true talent when the sample size is small?

1) So now it's "roughly" three seasons? So maybe it could be two for some guys and four for others? How do we differentiate who needs how many seasons?

2) We've agreed, somewhat, that 700 PA can sort of tell us who can knock the **** out of the ball and who can't. Why are you now using 50?

2b) Please see 2.

1) I don't see why you need an exact number. For OPS to reflect true talent you need roughly 600 PA (and even then it should be regressed 30% if you have just that 600 PA). Batting average needs over 900 PA (or roughly one and a half years). Everything is roughly. There are no absolutes. And I'm fairly certain that if I tried to tell you there were, you'd **** yourself.

2) If a guy only has 50 or 200 or 400 plate appearances, you wouldn't take his OPS or batting average or whatever offensive stat as his true talent level. You'd regress it to the mean by the appropriate amount because your sample is too small. At 600 plate appearances, OPS is fairly reliable (you'd need to get to over 900 for batting average), but the year to year correlation is still well below 1. To get to a similar correlation with UZR, you need three years of data because defensive opportunities don't happen as often as plate appearances.